The U.S. stock market concluded its worst year since the global financial crisis on Monday following a late-season collapse that also raised doubts about the prospects for 2019. 

Major indices notched modest gains in the year's final session, but it barely made a dent compared with the rest of December, the market's worst month in nearly a decade. 

The Dow Jones Industrial Average finished the final session with a gain of 1.2 percent, but finished 2018 with a loss of 5.6 percent compared to the end of 2017. The S&P 500 dropped 6.2 percent and the Nasdaq 3.9 percent.

That was after a year in which their indices jumped 25.1 percent, 19.4 percent and 28.2 percent. Wall Street marked the longest-ever "bull market" in August, a run that began amid extraordinary crisis-era monetary policy but for which Trump has claimed credit after his tax cuts and regulatory rollbacks.

The market confidence did not last due to slowing global growth, Italy's fiscal woes, a U.S. government shutdown and Trump's attacks on the Fed, the declines rapidly accelerated in the final weeks of 2018, erasing all the gains since January.

A U.S. government shutdown over Trump's desire to fund a wall along the border with Mexico extended into 2019 also has dented sentiment, especially amid signs economic growth has peaked.

Return to recession?

"To be clear, the challenges we see ahead don't look to us like the makings of another financial crisis," JPMorgan Private Bank said in a recent investor note. 

"Our base case assumes slowing growth in the U.S. economy throughout 2019 and a moderate recession in 2020," it continued.

"2018 has been characterized by a shift from low volatility, high liquidity and expectations of equity out-performance to high volatility, low liquidity and the return of a bear market in equities," said VTB Capital economist Neil MacKinnon.

"For 2019, a global economic slowdown, perhaps recession, looks increasingly likely," he warned.